/* SPDX-FileCopyrightText: 2023 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

/** \file
 * \ingroup bmesh
 *
 * Create faces or edges (F-key by default).
 */

#include "MEM_guardedalloc.h"

#include "BLI_listbase.h"

#include "bmesh.hh"

#include "intern/bmesh_operators_private.hh" /* own include */

#define ELE_NEW 1
#define ELE_OUT 2

void bmo_contextual_create_exec(BMesh *bm, BMOperator *op)
{
  /* NOTE(@ideasman42): doing the best thing here isn't always easy create vs dissolve,
   * its nice to support but it _really_ gives issues we might have to not call dissolve. */

  BMOIter oiter;
  BMHeader *h;
  int totv = 0, tote = 0, totf = 0;
  const short mat_nr = BMO_slot_int_get(op->slots_in, "mat_nr");
  const bool use_smooth = BMO_slot_bool_get(op->slots_in, "use_smooth");

  /* count number of each element type we were passe */
  BMO_ITER (h, &oiter, op->slots_in, "geom", BM_VERT | BM_EDGE | BM_FACE) {
    switch (h->htype) {
      case BM_VERT:
        BMO_vert_flag_enable(bm, (BMVert *)h, ELE_NEW);
        totv++;
        break;
      case BM_EDGE:
        BMO_edge_flag_enable(bm, (BMEdge *)h, ELE_NEW);
        tote++;
        break;
      case BM_FACE:
        BMO_face_flag_enable(bm, (BMFace *)h, ELE_NEW);
        totf++;
        break;
    }
  }

  /* --- Support Edge Creation ---
   * simple case when we only have 2 verts selected.
   */
  if (totv == 2 && tote == 0 && totf == 0) {
    BMVert *verts[2];
    BMEdge *e;

    if (BMO_iter_as_array(op->slots_in, "geom", BM_VERT, (void **)verts, 2) == 2) {
      /* create edge */
      e = BM_edge_create(bm, verts[0], verts[1], nullptr, BM_CREATE_NO_DOUBLE);
      BMO_edge_flag_enable(bm, e, ELE_OUT);
      tote += 1;
      BMO_slot_buffer_from_enabled_flag(bm, op, op->slots_out, "edges.out", BM_EDGE, ELE_OUT);
    }
    return;
  }

  /* --- Support for Special Case ---
   * where there is a contiguous edge ring with one isolated vertex.
   *
   * This example shows 2 edges created from 3 verts
   * with 1 free standing vertex. Dotted lines denote the 2 edges that are created.
   *
   * note that this works for any sided shape.
   *
   * +--------+
   * |        .
   * |        .
   * |        .
   * |        .
   * +........+ <-- starts out free standing.
   */

  /* Here we check for consistency and create 2 edges */
  if (totf == 0 && totv >= 4 && totv == tote + 2) {
    /* find a free standing vertex and 2 endpoint verts */
    BMVert *v, *v_free = nullptr, *v_a = nullptr, *v_b = nullptr;
    bool ok = true;

    BMO_ITER (v, &oiter, op->slots_in, "geom", BM_VERT) {
      /* count how many flagged edges this vertex uses */
      const int tot_edges = BMO_iter_elem_count_flag(bm, BM_EDGES_OF_VERT, v, ELE_NEW, true);
      if (tot_edges == 0) {
        /* only accept 1 free vert */
        if (v_free == nullptr) {
          v_free = v;
        }
        else {
          ok = false;
        } /* only ever want one of these */
      }
      else if (tot_edges == 1) {
        if (v_a == nullptr) {
          v_a = v;
        }
        else if (v_b == nullptr) {
          v_b = v;
        }
        else {
          ok = false;
        } /* only ever want 2 of these */
      }
      else if (tot_edges == 2) {
        /* do nothing, regular case */
      }
      else {
        ok = false; /* if a vertex has 3+ edge users then cancel - this is only simple cases */
      }

      if (ok == false) {
        break;
      }
    }

    if (ok == true && v_free && v_a && v_b) {
      BMEdge *e;

      e = BM_edge_create(bm, v_free, v_a, nullptr, BM_CREATE_NO_DOUBLE);
      BMO_edge_flag_enable(bm, e, ELE_NEW);

      e = BM_edge_create(bm, v_free, v_b, nullptr, BM_CREATE_NO_DOUBLE);
      BMO_edge_flag_enable(bm, e, ELE_NEW);
      tote += 2;
    }
  }
  /* --- end special case support, continue as normal --- */

  /* -------------------------------------------------------------------- */
  /* EdgeNet Create */
  if (tote != 0) {
    /* call edgenet prepare op so additional face creation cases work */

    BMOperator op_sub;
    BMO_op_initf(bm, &op_sub, op->flag, "edgenet_prepare edges=%fe", ELE_NEW);
    BMO_op_exec(bm, &op_sub);
    BMO_slot_buffer_flag_enable(bm, op_sub.slots_out, "edges.out", BM_EDGE, ELE_NEW);
    BMO_op_finish(bm, &op_sub);

    BMO_op_initf(bm,
                 &op_sub,
                 op->flag,
                 "edgenet_fill edges=%fe mat_nr=%i use_smooth=%b sides=%i",
                 ELE_NEW,
                 mat_nr,
                 use_smooth,
                 10000);

    BMO_op_exec(bm, &op_sub);

    /* return if edge net create did something */
    if (BMO_slot_buffer_len(op_sub.slots_out, "faces.out")) {
      BMO_slot_copy(&op_sub, slots_out, "faces.out", op, slots_out, "faces.out");
      BMO_op_finish(bm, &op_sub);
      return;
    }

    BMO_op_finish(bm, &op_sub);
  }

  /* -------------------------------------------------------------------- */
  /* Dissolve Face */
  if (totf != 0) { /* should be (totf > 1)... see below */
    /* NOTE: allow this to run on single faces so running on a single face
     * won't go on to create a face, treating them as random */
    BMOperator op_sub;
    BMO_op_initf(bm, &op_sub, op->flag, "dissolve_faces faces=%ff", ELE_NEW);
    BMO_op_exec(bm, &op_sub);

    /* if we dissolved anything, then return */
    if (BMO_slot_buffer_len(op_sub.slots_out, "region.out")) {
      BMO_slot_copy(&op_sub, slots_out, "region.out", op, slots_out, "faces.out");
      BMO_op_finish(bm, &op_sub);
      return;
    }

    BMO_op_finish(bm, &op_sub);
  }

  /* -------------------------------------------------------------------- */
  /* Fill EdgeLoop's - fills isolated loops, different from edgenet */
  if (tote > 2) {
    BMOperator op_sub;
    /* NOTE: in most cases 'edgenet_fill' will handle this case since in common cases
     * users fill in empty spaces, however its possible to have an edge selection around
     * existing geometry that makes 'edgenet_fill' fail. */
    BMO_op_initf(bm, &op_sub, op->flag, "edgeloop_fill edges=%fe", ELE_NEW);
    BMO_op_exec(bm, &op_sub);

    /* return if edge loop fill did something */
    if (BMO_slot_buffer_len(op_sub.slots_out, "faces.out")) {
      BMO_slot_copy(&op_sub, slots_out, "faces.out", op, slots_out, "faces.out");
      BMO_op_finish(bm, &op_sub);
      return;
    }

    BMO_op_finish(bm, &op_sub);
  }

  /* -------------------------------------------------------------------- */
  /* Continue with ad-hoc fill methods since operators fail,
   * edge, vcloud... may add more */

  if (false) { /* nice feature but perhaps it should be a different tool? */

    /* tricky feature for making a line/edge from selection history...
     *
     * Rather than do nothing, when 5+ verts are selected, check if they are in our history,
     * when this is so, we can make edges from them, but _not_ a face,
     * if it is the intention to make a face the user can just hit F again
     * since there will be edges next time around.
     *
     * if all history verts have ELE_NEW flagged and the total number of history verts == totv,
     * then we know the history contains all verts here and we can continue...
     */
    int tot_ese_v = 0;

    LISTBASE_FOREACH (BMEditSelection *, ese, &bm->selected) {
      if (ese->htype == BM_VERT) {
        if (BMO_vert_flag_test(bm, (BMVert *)ese->ele, ELE_NEW)) {
          tot_ese_v++;
        }
        else {
          /* unflagged vert means we are not in sync */
          tot_ese_v = -1;
          break;
        }
      }
    }

    if (tot_ese_v == totv) {
      BMVert *v_prev = nullptr;
      /* yes, all select-history verts are accounted for, now make edges */

      LISTBASE_FOREACH (BMEditSelection *, ese, &bm->selected) {
        if (ese->htype == BM_VERT) {
          BMVert *v = (BMVert *)ese->ele;
          if (v_prev) {
            BMEdge *e = BM_edge_create(bm, v, v_prev, nullptr, BM_CREATE_NO_DOUBLE);
            BMO_edge_flag_enable(bm, e, ELE_OUT);
          }
          v_prev = v;
        }
      }
    }
    BMO_slot_buffer_from_enabled_flag(bm, op, op->slots_out, "edges.out", BM_EDGE, ELE_OUT);
    /* done creating edges */

    return;
  }

  /* -------------------------------------------------------------------- */
  /* Fill Vertex Cloud
   *
   * last resort when all else fails.
   */
  if (totv > 2) {
    /* TODO: some of these vertices may be connected by edges,
     * this connectivity could be used rather than treating
     * them as a bunch of isolated verts. */

    BMVert **vert_arr = static_cast<BMVert **>(MEM_mallocN(sizeof(BMVert *) * totv, __func__));
    BMFace *f;

    totv = BMO_iter_as_array(op->slots_in, "geom", BM_VERT, (void **)vert_arr, totv);

    BM_verts_sort_radial_plane(vert_arr, totv);

    /* create edges and find the winding (if faces are attached to any existing edges) */
    f = BM_face_create_ngon_verts(bm, vert_arr, totv, nullptr, BM_CREATE_NO_DOUBLE, true, true);

    if (f) {
      BMO_face_flag_enable(bm, f, ELE_OUT);
      f->mat_nr = mat_nr;
      if (use_smooth) {
        BM_elem_flag_enable(f, BM_ELEM_SMOOTH);
      }
      BM_face_copy_shared(bm, f, nullptr, nullptr);
      BMO_slot_buffer_from_enabled_flag(bm, op, op->slots_out, "faces.out", BM_FACE, ELE_OUT);
    }

    MEM_freeN(vert_arr);
  }
}
